Dynamometer



Nov. 16, 1937. .1. c. SLONNEGER 2,099,662

DYNAMOMETEE Filed April 13, 1935 INVENTOR. John. C. Slonneger;

A TTORNE Y.

Patented Nov. 16, 1937 UNITED STATES PATENT QFFICE DYNAMOMETER John C. Slonnegcr, Milwaukee, Wis., assignor to The Falk Corporation, Milwaukee, Wis., a corl poration of Wisconsin Application April 13, 1935, Serial No. 16,181

Claims. (01. 265-1) This invention relates to dynamometers for use I4, is seated for longitudinal adjustment upon primarily in ascertaining the operating stresses and along the plate I3 between the clamps Ill and in oil well pump rods, although the invention also II. The carriage is guided by suitable means may be used to advantage in ascertaining the such as a longitudinal rib l5 closely fitted within 5v longitudinal stresses involved in other parts of a slot I6 provided in the plate I3, and is releasoil Well and other equipment, particularly those ably fixed in any position of adjustment by a subjected to severe and variable loads. clamp screw I! which extends through a clamp It has been found that knowled of the plate I8 into the base of the carriage.

Stresses in D p rods, and particularly of the The clamp II is similarly guided upon the plate 10 magnitude and nature of the stress changes which l3 and similarly adjustably fixed thereto by a occur therein during a complete pump stroke clamp Screw l9 d clamp m t 2u ycle, is of imm se V ue in determining the Mechanism is provided on the carriage [4 for length, range, and frequency of a p p Stroke coaction with the clamp I l to accurately indib adapted for y given installation That cate the magnitude of microscopic movement beis t say, th st ss chan s whi c u n apump tween the clamp and carriage. This mechanism 15 rod at the head of a well constitute an accurate inchldes a microscopic gauge 2 of type reflection of the pump action at the bottom of monly known i machine shop practice as a the well, and when accurately ascertained and al d t r", Th gauge is shown rigidly supp ly t p d t y a d a reliable guide ported by a bracket 22, fixed to the carriage I4, 26 to the ettalhment Of a most effi'cieht D p and equipped with a rotary pointer 23 which retlohi sponds to slight longitudinal movement of the An ObJeCt 0f the Present Invention is the P stem 24, with which such gauges are commonvision of a simple and inexpensive dynamometer 1 equipped, It i l o equipped with the cus- Which may be r a ily pp to a pump Tod tomary dial 25 adjustably fixed by the usual ele- 25 the like and which will reliably indicate the magt 26, 25 nltude 0f t Stresses e n u i and In this instance the stem 24 bears against the t r u hout a co p e e op a cy e. spherical end head 21 of the long arm of a mo- Another j c is to provide a dynamome tion multiplying lever 28, which is rockably supcf the character described which ay be appli d ported intermediate its ends upon a pin 29 fixed 30 to a P p mechanism Without in ny manner in the carriage M. The other short arm of the 3 affecting e peration or operating characterislever terminates in a spherical end head 30 artics of the latter, so that a true indication of the ranged to bear against the flat end of a lug 3| stresses therein may be had during truly normal which projects from the clamp H. Any appro- Operetion thereofpriate means such as a spring 32 acts on the lever Other objects a d ad an a es l appear. ex- 28 in a direction to urge the stem 24 inwardly. 35 pressed or implied, from the following descrip- Both clamps l0 and H are preferably of the tion of a dynamometer constructed in accordance v type, each comprising a pair of stationary h t P s inventionjaws 33 and 34, preferably disposed at right angles In h ac mpan in drawing: to each other with one of the jaws '33 extending Figure 1 is a side elevation, partly in section, crosswise of the plate 13 and parallel to the plane 40 of a dynamometer embodying the present inventhereof. The gripping face of each jaw is retion and showing the same applied to the polish lieved by a central longitudinal channel 35 so red of an 011 Well p pas to form spaced longitudinal lands 36 and 31 g. 2 is a front elevation. adjacent the opposite edges thereof. Fig. 3 is a sectional view on the line 3-3 of Each clamp shown also includes a clamp bar 45 1. 38 carried by a pair of parallel studs 39 which The y em Shown Comprises a P of project angularly from the outer ends of the jaws clamps l0 and II for application to the polish'rod 33 and 34 and which are threaded to receive apl2 of an oil well pump. The clamps are adjustably propriate clamp nuts 46. It will be noted that the 50 connected y ppropriate means such as a metal axes of studs 39 of each clamp lie in a plane plate l3. In this instance the plate [3 is fixed at nearer to the inner lands 36 of the jaws than one end to one of the clamps I0 and adjustably to the outer lands 3! thereof, so that the inner engaged adjacent its other end with the other lands 36 sustain the major portion of the clampclamp II. ing pressure, for a purpose which will later A carriage, preferably in the form of a. block appear, w

In preparing the device for use on any particular rod I2, the clamp II is first temporarily fixed at a definite position upon the plate I3 so as to provide a predetermined spacing between the clamps I0 and II, the spacing selected being dependent upon the size of the rod. For convenience the plate I3 may be graduated as a guide to the proper positioning of the clamp II. The device is then applied to the rod and both clamps rigidly secured thereto by tightening the nuts 40 against the bars 38. Thereafter the clamp H is released from the plate I3 by releasing the screw I9, and the carriage I4 is advanced along the plate I3 until the head 30 of the lever is displaced slightly by engagement with the lug 3I on the clamp II, in which position the carriage I4 is fixed to the plate I3 by tightening the screw I1.

It will be noted that with the parts arranged in the manner just described the carriage I4 is fixed relative to the clamp I0, and that the other clamp II is movable relative to the carriage in response to changes in the length of that section of the rod between the clamps I0 and II. This relative movement between the clamp II and carriage I4 is multiplied and transmitted by and through the lever 28 to the stem 24 of the indicator, so that the pointer 23 moves accordingly. It is of course understood that in a rod section of given length and diameter, the changes in length are proportional to the stresses which induce those changes, so that the movements of the pointer 23 are proportional to the stresses in the rod.

The variable spacing between the clamps I0 and I I makes it possible to obtain from the indicator a direct reading of the amount of stress in the rod, regardless of the size of the rod to which the device is attached. The extent of elongation of the rod section, and consequent actuation of the indicator induced by a particular stress, is of course inversely proportional to the cross sectional area of that section and directly proportional to the length of the section, but by adjusting the clamps so as to change the length of the rod section comprised between them, due compensation is made for variations in rod sizes.

To determine the magnitude of the operating stresses in the polish rod of an oilwell pump, the device is applied to the rod in the manner above described while the pump is at rest, the clamps i0 and II being spaced apart a predetermined distance dependent upon the size of the rod. The stress set up in this rod by the dead weight of the pump rods supported thereby may of course be computed and the dial 25 may be manually adjusted in a well known manner to indicate the value of that stress, and then when the pump is operated the indicator will accurately show the true stresses in the rod throughout each pump stroke cycle. Or the dial 25 may be set at zero, when the pump is at rest, in which event the indicator will show the rise and fall of the stresses in the rod during operation of the pump.

It will be noted that in the device shown the end head 30 of the lever is disposed as close as practicable to the rod I2 and within or close to that plane which passes through the axis of the rod and normal to the plate I3. In this position the lever 23 and indicator are unaffected by any bending of the rod that may occur in a plane parallel to the plate, although bending of the rod in a plane normal to the plate would disturb the lever and introduce an error in the dial reading. Since the only bending which occurs in a polish rod during pump operation is in a plane through the rod and walking beam, the device is ordinarily applied to the rod in such position that the plate I3 is disposed parallel to the plane last mentioned. This arrangement eliminates all possibility of error in indicator readings that might otherwise result from such causes.

As previously pointed out the clamping pressure between the rod and the clamp jaws 33 and 34 is sustained largely by the lands 36, the other lands 3'! of the jaws merely serving to properly position the jaws at right angles to the axis of the rod. This arrangement permits the rod to slip relative to the lands 3! as it expands and contracts in response to variations in the stresses in it, without disturbing the fixed grip of the lands 36 on the rod. This eliminates any tendency of the clamps to creep along the rod. Furthermore the lands 36 provide rather narrow areas of contact with the rod so that the length of rod comprised between them is nicely defined.

The device is shown applied to a rod of relatively large size. When used on a smaller rod I2, a block 4|, shown in dotted lines in Fig 3, is preferably interposed between the rod I2 and the jaw 34 of each clamp, so that the end head 30 of the lever 28 lies in a plane passing through the axis of the rod and normal to the plate I3.

Various changes may be made in the embodiment of the invention hereinabove specifically described without departing from or sacrificing the advantages of the invention as defined in the appended claims.

I claim:-

1. A dynamometer for measuring stresses in a rod-like member, said dynamometer comprising a pair of spaced clamps engageable with said member and relatively movable in response to stress changes in said member, and means for indicating the extent of such movement between said clamps, each of said clamps having a jaw engageable with said member at points spaced longitudinally of said member, and means for inducing a clamping pressure between said jaw and member, said last named means being arranged so that the major portion of said clamping pressure is sustained at one of said spaced points.

2. A dynamometer for measuring stresses in a rod-like member, said dynamometer comprising a pair of spaced clamps for application to said member, a connection between said clamps adjustable to determine the initial spacing thereof and releasable to permit relative movement between said clamps in response to stress changes in said member, means responsive to relative movement between said clamps for indicating the magnitude of stress changes in said member, and a carrier for said means adjustably mounted on said connection to render said means effective in the various spaced positions of said clamps.

3. A dynamometer for measuring stresses in a rod-like member, said dynamometer comprising a pair of spaced clamps for application to said member, a connection between said clamps for positioning and aligning the same preparatory to applying the same to said member, said connection being adjustable to vary the spacing between said clamps in accordance with the cross sectional area of said member, and said connection being releasable after application of said clamps to said member to permit relative move- 'ment between said clamps in response to stress changes in said member, and means supported by said connection and responsive to such relative movement for indicating the magnitude of stress changes in said member, said means being adjustable relative to both of said clamps to render said means effective in the various spaced positions of said clamps.

4. A dynamometer for measuring stresses in a rod-like member, said dynamometer comprising a pair of spaced clamps for application to said member, a member for positioning and aligning the said clamps preparatory to applying the same i to said first named member, means for temporarily fixing one of said clamps at any of a plurality of points along said last named member to vary the spacing between said clamps in accordance with the cross sectional area of said first named member, said means being releasable to permit relative movement between said last named clamp and said last named member in response to stress changes in said first named member, and means adjustably fixed to said last named member and coacting with said last named clamp for indicating the magnitude of stress changes in said first named member.

5. A dynamometer for measuring stresses in a rod-like member, said dynamometer comprising a pair of spaced clamps for application to said member, a plate fixed to one of said clamps and slidably engaged in guiding relation with the other of said clamps, means for temporarily fixing said last named clamp at any of a plurality of points along said plate, said means being releasable to permit relative movement between said last named clamp and said plate in response to stress changes in said member, a carrier adjustably fixed to said plate, and means on said carrier coacting with said last named clamp for indicating the stress changes in said member.

JOHN C. SLONNEGER. 

